[PATCH bpf 8/9] selftests/bpf: Add write tests for sk storage map iterator

[Hou Tao <houtao@xxxxxxxxxxxxxxx>]

From: Hou Tao <houtao1@xxxxxxxxxx>

Add test to validate the overwrite of sock storage map value in map
iterator and another one to ensure out-of-bound value writing is
rejected.

Signed-off-by: Hou Tao <houtao1@xxxxxxxxxx>
---
 .../selftests/bpf/prog_tests/bpf_iter.c       | 20 +++++++++++++++++--
 .../bpf/progs/bpf_iter_bpf_sk_storage_map.c   | 20 ++++++++++++++++++-
 2 files changed, 37 insertions(+), 3 deletions(-)

diff --git a/tools/testing/selftests/bpf/prog_tests/bpf_iter.c b/tools/testing/selftests/bpf/prog_tests/bpf_iter.c
index 94c2c8df3fe4..f75308d75570 100644
--- a/tools/testing/selftests/bpf/prog_tests/bpf_iter.c
+++ b/tools/testing/selftests/bpf/prog_tests/bpf_iter.c
@@ -1074,7 +1074,7 @@ static void test_bpf_sk_stoarge_map_iter_fd(void)
 	if (!ASSERT_OK_PTR(skel, "bpf_iter_bpf_sk_storage_map__open_and_load"))
 		return;
 
-	do_read_map_iter_fd(&skel->skeleton, skel->progs.dump_bpf_sk_storage_map,
+	do_read_map_iter_fd(&skel->skeleton, skel->progs.rw_bpf_sk_storage_map,
 			    skel->maps.sk_stg_map);
 
 	bpf_iter_bpf_sk_storage_map__destroy(skel);
@@ -1115,7 +1115,15 @@ static void test_bpf_sk_storage_map(void)
 	linfo.map.map_fd = map_fd;
 	opts.link_info = &linfo;
 	opts.link_info_len = sizeof(linfo);
-	link = bpf_program__attach_iter(skel->progs.dump_bpf_sk_storage_map, &opts);
+	link = bpf_program__attach_iter(skel->progs.oob_write_bpf_sk_storage_map, &opts);
+	err = libbpf_get_error(link);
+	if (!ASSERT_EQ(err, -EACCES, "attach_oob_write_iter")) {
+		if (!err)
+			bpf_link__destroy(link);
+		goto out;
+	}
+
+	link = bpf_program__attach_iter(skel->progs.rw_bpf_sk_storage_map, &opts);
 	if (!ASSERT_OK_PTR(link, "attach_iter"))
 		goto out;
 
@@ -1123,6 +1131,7 @@ static void test_bpf_sk_storage_map(void)
 	if (!ASSERT_GE(iter_fd, 0, "create_iter"))
 		goto free_link;
 
+	skel->bss->to_add_val = time(NULL);
 	/* do some tests */
 	while ((len = read(iter_fd, buf, sizeof(buf))) > 0)
 		;
@@ -1136,6 +1145,13 @@ static void test_bpf_sk_storage_map(void)
 	if (!ASSERT_EQ(skel->bss->val_sum, expected_val, "val_sum"))
 		goto close_iter;
 
+	for (i = 0; i < num_sockets; i++) {
+		err = bpf_map_lookup_elem(map_fd, &sock_fd[i], &val);
+		if (!ASSERT_OK(err, "map_lookup") ||
+		    !ASSERT_EQ(val, i + 1 + skel->bss->to_add_val, "check_map_value"))
+			break;
+	}
+
 close_iter:
 	close(iter_fd);
 free_link:
diff --git a/tools/testing/selftests/bpf/progs/bpf_iter_bpf_sk_storage_map.c b/tools/testing/selftests/bpf/progs/bpf_iter_bpf_sk_storage_map.c
index 6b70ccaba301..6a82f8b0c0fa 100644
--- a/tools/testing/selftests/bpf/progs/bpf_iter_bpf_sk_storage_map.c
+++ b/tools/testing/selftests/bpf/progs/bpf_iter_bpf_sk_storage_map.c
@@ -16,9 +16,10 @@ struct {
 
 __u32 val_sum = 0;
 __u32 ipv6_sk_count = 0;
+__u32 to_add_val = 0;
 
 SEC("iter/bpf_sk_storage_map")
-int dump_bpf_sk_storage_map(struct bpf_iter__bpf_sk_storage_map *ctx)
+int rw_bpf_sk_storage_map(struct bpf_iter__bpf_sk_storage_map *ctx)
 {
 	struct sock *sk = ctx->sk;
 	__u32 *val = ctx->value;
@@ -30,5 +31,22 @@ int dump_bpf_sk_storage_map(struct bpf_iter__bpf_sk_storage_map *ctx)
 		ipv6_sk_count++;
 
 	val_sum += *val;
+
+	*val += to_add_val;
+
+	return 0;
+}
+
+SEC("iter/bpf_sk_storage_map")
+int oob_write_bpf_sk_storage_map(struct bpf_iter__bpf_sk_storage_map *ctx)
+{
+	struct sock *sk = ctx->sk;
+	__u32 *val = ctx->value;
+
+	if (sk == (void *)0 || val == (void *)0)
+		return 0;
+
+	*(val + 1) = 0xdeadbeef;
+
 	return 0;
 }
-- 
2.29.2